Income Taxes - Deferred tax assets (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforward	$ 505,000	$ 493,000
Allowance for doubtful accounts	0	14,000
Revenue recognition	66,000	66,000
Less valuation allowance	(571,000)	(573,000)
Net deferred tax asset	$ 0	$ 0